Variable capacity compressor control



Dec. 15, 1942. R. A. GONZALEZ 2,304,999

VARIABLE CAPACITY COMPRESSOR ONTROL med Feb. 14, 1941 4 sheets-sheet 1 Q INVENTOR 1 l gawfzzudz.

Dec. l5, 1942. R, A GONZALEZ 2,304,999

VARIABLE CAPACITY COMPRESSOR CONTROL Filed Feb. 14, 1941 f 4 Sheets-Sheet 2 De. 15, 1942. R. A. GONZALEZ 2,304,999

VARIABLE CAPACITY COMPRESSOR CONTROL Filed Feb. 14, 1941 4 Sheets-Sheet 5 'f BY ATTORN EY5 Dec. 15, 1942. R. A. GONZALEZ VARIABLE CAAGITY COMPRESSOR CONTROL Filed Feb. 14, 1941 4 Sheets-Sheet 4 .mMHl

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Patent'ed Dec. 15, 1942 VARIABLE CAPACITY COMPRESSOR f CONTROL Rafael A. Gonzalez, Dayton, Ohio, assigner to Chrysler Corporation, Detroit, Mich., a corporation of Delaware Application February 14, 1941, Serial No. 378,935

7 Claims.

My present invention relates to the arts of refrigeration and air conditioning, the invention being applicable to a refrigerating system of the compressor-condenser-evaporator type whether the system be used to cool and dehumidify air for air conditioning purposes or to chill a medium surrounding the evaporator, such as air, salt brine, or a liquid such as 'diethylene glycol, which medium would be used for the purpose of preserving foodstuffs, producing ice. or any other purpose for which refrigerating systems are of utility.

'I'he present invention is of particular application to a refrigerating system including a compressor of the type disclosed and claimed in the patent to Charles R. Neeson, No. 2,185,473, issued January 2, 1940, the present invention including a device responsive to the temperature of the air being conditioned or the temperature of the medium surrounding the evaporator coil for effecting unloading and loading of the compressor of the refrigerating system in response to a temperature condition.

Specifically, the present invention comprises means including an air pressure control system having a part located in the medium being cooled for operating a pressure regulating valve so as to regulate the air pressure transmitted to the operator of a variable capacity producing means in a compressor, whereby to vary the capacity of the compressor with the load on the evaporator served by the compressor.

The invention will be more fully understood by study of the following specification taken in connection with the accompanying drawings wherein like numerals refer to like parts throughout. In the drawings, Fig. 1 discloses an air conditioning system having the present invention applied thereto, the compressor disclosed therein being of the type covered by the aforesaid patent to Neeson;

Fig. 2 is a longitudinal section through a compressor having the present invention associated therewith, and showing details of the capacity varying means disclosed in the aforesaid patent to Neeson;

Fig. 3 is a view in elevation of the front cover of the compressor disclosed in Fig. 2, with details of the capacity regulating master valve and the operating mechanism of the present invention attached thereto;

Fig. 4 is an end view of the portion of the apparatus disclosed in Fig. 3;

Fig. 5 is a sectional view taken through the master valve mechanism and the operating mechanism; and,

Fig. 6 is a partial view of a modification in part of the apparatus disclosed in Fig. 5.

is expanded into an evaporator 23 having connection to the inlets of both compressors. Therefore, for all practical purposes the two compressing units may be considered as a single compresser. 'I'he evaporator 23 is located in a duct 24 through which a stream of air is drawn by a blower 25, the air `passing over the evaporator being cooled and dehumidifled andbeing then discharged into the space to be served by the action of the blower. It is, of course, readily apparent that the evaporator may be located in a food storage compartment over which air is circulated by av blower means or by gravity, or in a medium of liquid type used for various cooling purposes.

Details of one of the compressing units are disclosed in Fig. 2 wherein it is seen that the compressing unit 20 comprises a crankshaft 30 to which are connected a plurality of connecting rods 3| each operating a. piston 32 in a cylinder 33. Gas which is admitted to the suction manifold 34 from the evaporator 23 passes into the interior of the cylinder through the suction valve 35 and is ejected through the discharge valve 36 into the discharge head 31 which is connected by passage 38 to the common discharge manifold 39 from which the compressed gas passes into the condenser 22. Details of the valve and piston construction may be ascertained from the aforesaid patent to Neeson, as well as the patent to Charles R. Neeson, No. 2,137,965, issued November 22, 1938.

As further explained in the aforesaid Patent No. 2,185,473, the suction manifold 34 is connected through ports Vlll with the interior space il of the crankcase whereby a llexible, metallic bellows 42 is subjected to the pressure of the expanded refrigerant returned from the evaporator. Movement of the bellows 42 causes reciprocation of a linkrod 43 connected by rocking levers 44 to a master valve member 45. The master valve member 45 (Fig. 5) is provided with a plurality of notches so that a spring pressed ball 5| engaging in the notches permits step-by-step movement of the master valve member. Each step causes one o f a plurality of slots 52 to be con- 2 I accesos of a ring 59 having unloader pins CII mounted 10 thereon, which when moved radially outward cause the suction valve Ii to beheld open continuously whereby the cylinder is unloaded or prevented from compressing refrigerant. The position of the variably movable valve part 45, therefore, controls the number of unloader pistons 54 to which oil pressure is applied, and hence controls the number of cylindersv in operation. When, as disclosed in Fig. 5, all but one of the slots I2 `are connected to tube Il through the annular space 6| surrounding the reduced portion of valve member 4l, all but one oi the individual cylinders will be loaded or operating. When valve member 45 is moved inwardly the length ot another notch 50, two cylinders will be unloaded since another one of the unloader cylinders 55 will be disconnected from the source of oli pressure. Oil pressure is applied to the unloading mechanism through the master valve from a pressure lubricating pump v(not shown). details of which may be ascertained from the aforesaid Neeson Patent No. 2,185,473.v Asdisclosed in the' aforesaid patent. the oil pressure pump operates coextensively with operation of motor 2| Vso that no oil pressure will be supplied to the master valve 24 unless the motor is operating, and since it takes a short while for the pressure to be built up by the oil pump it is apparent that all cylinders will be unloaded duringstarting, thereby preventing large starting current. inrush. It is also apparent that after oil pressureis available a number oi' cylinders vwill be unloaded depending upon the position oi the linkrod 43.

The aforesaid Neeson Patent No. 2,185,473, discloses that the position of linkrod 43 may be controlled by the degree of compression of the ilexible, metallic bellows 42, whichrcompression is effected by the pressure of the gas in the space 4I connected to the suction side of the refrigerating system through the port 40,- The pressure of the gas against bellows 42 operates against a compression spring 65 positioned between the end of the bellows and an adjusting mechanism 66. In the aforesaid patent. it is explained that the compression of. the spring 65 controls the unloading pressure of the master valve so that the suction pressure of the refrigerating system may be controlled within reasonable limits. However, it has been found in air being conditioned, or the medium surround ing the evaporator, varies. In this manner i reduce the reaction time of the compressor to a great extent and enable more accurate control oi' a desired temperature condition.

As seen in Fig. 1, I provide an air pressure control system including an air compressor 1ldischarging into a pressure tank 1|. A pipe 12 discharges compressed air from the tank 1| into a pressure regulating valve 12 including a iixed orince 14. The orifice 'I4 maintains a steady discharge of compressed air at a constant presrsure depending upon the pressure maintained in tank 1I by some such device as a safety blowoff 1I. The space 1I into which oriiice 14 discharges is connected by pipes 11 and 1I, respectively, to master valve operators 19 and 90. respectively, each controlling one of the master valves 26. The pressure exerted by the master valve operators is controlled by regulating the pressure in space 10, which is accomplished by varying the amount of air permitted to escape through a variable orifice valve comprising a plunger 9| operated by a diaphragm 82 and return spring 83. The position of the plunger Il is controlled by the pressure in -a thermostatic bulb 84 connected to the space of which diaphragm 82 comprises a movable wall and which contains a iluid reacting to the temperature of the air or iluid medium surrounding the bulb. 'As the temperature rises, diaphragm 92 is depressed and the pressure in space 16 drops as a result of increased opening of the valve controlled by plunger Il. 'I'he valve 13 is schematically disclosed herein, but several types are readily available whereby a change in temperature of one degree may produce a drop in pressure in space 16 of one pound, or other readily calibrated pressure drop.

As seen in Fig. 5, tube 18 is connected through an oriilce 90 to a space 9| of which a diaphragm 92 forms a movable wall. The diaphragm 92 is vulcanized or otherwise secured to a plate 93 to which is fastened an operating rod 94. A guide member and spring retainer 95 surrounds the rod and moves coextensively therewith, the same serving to retain a compression spring 96 compressed between the diaphragm 92 and a portion of the housing 91 for the diaphragm and spring. The operating rod 94 abuts the outer end of an extension of linkrod 43 and thereby causes movement of the master valve part 45.' 'I'he pressure exerted by the air pump through tube 18, the size of diaphragm 92, and the compression strength of spring 96 are preferably so selected as to render the effect of spring negligible, so that complete inward movement of the linkrod 43 is controlled entirely by the degree of air pressure in tube 18 which is immesome instances that the pressure of the gas returning to the compressor does not cause the compressor unloading mechanism to react fast enough to suit the conditions for which the system is designed, as changes in the. suction pressure may lag behind the changes `in a temperature condition produced by the evaporator.. Accordingly, I have devised means for eliminating the eilect of the suction pressure upon the bellows 42 and for controlling the position of the master valve part 45 directly in response to the temperature of the mediumV surrounding the evaporator 23. By sucl` means Iam able to unload individual cylinders of the compressor, or to vary the capacity'oi' the compressor, practically instantaneously as the temperature of the diately responsive to the temperature of the air being conditioned o r the medium surrounding the evaporator. As seen in Fig. 5, the linkrod 43 abuts operating rod 94 within the connes of the guide member 95 so that the two need not be pinned together. In order that the linkrod 43 may be returned outward when spring 9S has returned operating rod 9d outward, bellows l2 has been maintained of sumcient diameter so that the pressure of the suction gas will compress v spring 65 and cause the end oi linkrod 153 to remain in contact with the end of operating rod 94. Ii the air pressure should fail or the thermostatic bulb 96 should need replacement, the po sition of llnkrod $3 would be then placed under control of the gas pressure, as fully elained in the aforesaid patent to Neeson No. 2,185,473. Hence, a feature of safety is introduced since it would require a complete failure of both the temperature responsive means and the suction responsive means to render the unloader mechanism ineective.

I have disclosed in Fig. 6 a modification whereby the end of operating rod I4 and the outer end of linkrod 43 are pinned together by shaping the respective ends and passing a pin ill through overlapping parts thereof. In such event there is no possibility of the suction pressure responsive bellows assuming control, hence the spring I5 has been removed. Therefore, with this modification failure of the temperature responsive means would be more readily indicated to the operator of the machine and immediate repairs could be made.

The operation of the present invention is as follows: The compressor forces hot refrigerant gas into the condenser where the refrigerant is liquefied at the condensing pressure. The refrigerant is expanded in the evaporator 23 'and extracts heat from the air or other surrounding medium. The expanded refrigerant is returned to the compressor and through the suction manifold 54 into the cylinders where it is again coinpressed. The suction pressure, which reflects the load on the evaporator, exerts pressure on the bellows 42 which tends variably to control the position of the unloader valve part 45. However, complete control of the unloader valve part 45 has been passed to the temperature responsive valve operator 19 or 80 by making the size of diaphragm 92 so great as to render the suction pressure effect on bellows 42 negligible, and by making the compressive force of spring 96 so great as to render the compressive force of spring 85 negligible. The position of the master valve part 45 is thus controlledby the temperature of the air or medium surrounding the evaporator which causes variable leakage from the space 16 connected to the air pressure tank.l As the air pressure in space 1B varies, the pressure against diaphragm 92 varies, causing inward or outward movement of the valve part 45 in steps controlled by the ball 5i riding in the notches 50. The movement of the master valve part 45 controls the connecting or disconnecting of one or more of the unloader cylinder spaces 55 and the source of iluid pressure through tubes 53 and 54. When pressure is applied to a cylinder space 55 the piston 56 therein is moved inward and causes the yoke 51 to ride down on ramp 58, thus dropping the pins 50 from the suction valve 35 and allowing the cylinder to compress gas. nection of the cylinder space 55 from the source of iluid pressure causes the cylinder to become loaded. In this manner the number of cylinders in operation varies so that the capacity of the compressor varies directly in response to the temperature produced by the evaporator.

If desired a pin ini may be placed in the master valve part 45 to prevent movement of the part 45 to such an extent as to unload all of the cylinders, thereby creating a system in which the compressor will always compress gas through one or more cylinders. This is desirable in a system wherein the load on the evaporator may drop to such an extent as to cause the compressor to compress gas through only one cylinder, drawing more current than the need for refrigeration warrants. With the pin lill in use the compressor will compress gas until such time as a reserve may be built up in the condenser suillcient Disconv to satisfy the light load for a considerable period of time, whereupon the usual safety devices (not shown) may cause the compressor to cease operating temporarily.

Having described a preferred embodiment of my invention it should be apparent to those skilled in the art that the same permits of modincations in arrangement and detail. All such as come within the scope of the following claims are considered a part of my invention.

I claim:

1. Unloading mechanism for a variable capacity compressor adapted to be connected to a cooling system and having a plurality of compressing cylinders, each of a number of which may be selectively rendered inoperative in order to vary the capacity of the compressor, comprising a plurality of individual cylinder unloading means each operatively associated with a single cylinder, fluid pressure creating means for operating said individual cylinder unloading means, means for selectively connecting said nuld pressure creating means to said individual cylinder unloading means comprising a master valve including a valve rod adapted to be selectively positioned at a plurality of positions, and means for selecting the position of said valve rod comprising a spring biased to move said valve rod in one direction, a collapsible bellows subjected to the suction pressure of said compressor and operating against said spring for returning said valve rod in the opposite direction to a plurality of successive positions when the suction presure rises successively above a number of predetermined pressures, fluid pressure operated means of greater force than that of said bellows to move said valve rod in said one direction against the force of said bellows even 'though the suction pressure may be above 'the highest of said predetermined pressures, and means to control the eacA tent of movement of said valve rod by said fluid pressure operated means comprising a pressure regulating device for regulating the fluid pressure exerted against said fluid pressure operated means and a temperature responsive mechanism responding to the temperature created by the action of the cooling system for variably controlling the setting of said pressure regulating device.

2. Unloading mechanism for a variable capacity compressoradapted to be connected to a cool ing system and having a plurality of compressing cylinders, each of a number of which may be selectively rendered inoperative in order to vary the capacity of the compressor, comprising a plurality of individual cylinder unloading means each operatively associated with a single cylinde.` fluid pressure creating means for operating said individual cylinder unloading means, means for selectively connecting said iluid pressure creating means to said individual cylinder unloading means comprising a master valve including a valve rod adapted to be selectively positioned at a plurality of positions, and means for selecting the position of said valve rod comprising a spring biased to move said valve rod in one direction, a collapsible bellows subjected to the suction pressure of said compressor and operating against said spring for returning said valve rod in the opposite direction to a plurality of successive positions when the suction pressure rises successively above a. number of predetermined pressures, fluid pressure operated means of greater force than that of said bellows to move said valve rod in said one direction against the force direction, and a second spring biased to move said plunger in the opposite direction, said plunger being disconnected from said valve rod whereby return movement of said valve rod in said opposite direction is accomplished by said bellows,

and means to control the extent of movement of said valve rod by said iluid pressure operated means comprising a pressure regulating devicev for regulating the iluid pressure exerted against said fluid pressure operated means and a temperature responsive mechanism responding to the temperature created by the action of the cooling system for variably controlling the setting of said pressure regulating device.

3. A cooling system comprising a compressorcondenser-evaporator systemV of refrigeration, the ycompressor oi which comprises a plurality of cylinders and means to vary the number of cylinders compressing refrigerant comprising individual cylinder unloading means associated with each of a number of said cylinders, iiuid pressure means for operating said individual1 cylinder unloading means including a. master valve having a valve rod capable of being moved to a number of control positions to vary the number lof said individual cylinder unloading means operatively connected to said iluid pressure means, and dual means for selecting the control position to which said valve rod is moved comprising a first valve rod operator including a part subjected to the suction pressure of said compressor for controlling the number of cylinders in operation in accordance with the suction pressure of the system and a second valve rod operator including a part subjected to the temperature of the medium cooled by said system for controlling the number of cylinders in operation by the temperature created by said system, each of said valve rod operators being capable oi independent operation but one of said valve rod operators being strong enough to overcome the action of the other of said valve rod operators.

4. A cooling system comprising a compressorcondenser-evaporator system of refrigeration, the compressor of which comprises a plurality of cylinders and means to vary the number of cylinders compressing refrigerant comprising individual cylinder unloading means associated with each of a number of -said cylinders, iluid pressure means for operating said individual cylinder unloading means including a master valve having a valve rod capable of being moved to a number of control positions to vary the number of said individual cylinder unloadingy means operatively connected to said fluid pressure means, and dual means for selecting the control position to which said valve rod is moved comprising a first valve rod operator including a part subjected to the suction pressure of said compressor for controlling the number of cylinders in operation in accordance with the suction pressure of the system and a second valve rod operator including a part subjected to the temperature, of the medium cooled by said system for controlling the number of cylinders in operation by the temperature created by said system, one of said valve rod operators being stronger than the other of said valve rod operators so` as completely to control the sition of d valve r in spite of the edect ofthe other valve rod operator, but each oi said valve rod operators being capable oi operating independently ot the other so that in case one iails the other will continue to control the position oi said valve rod.

5. A cooling system comprising a compressorcondenserevaporator system of refrigeration, the compressor oi. which comprises a plurality of cylinders and means to vary the number 'o'i cylinders compressing refrigerant comprising individual cylinder unloading means associated with each of a number of said cylinders, uid pressure means for operating said individual cylinder unloading means including a master valve having a valve rod capable of being moved to a number of control positions tovary the number of said individual cylinderunloading means operatively connected to said iluid pressure means. and dual means for selecting the control position to which said valve rod is moved comprising a rst valve rod operator including a. part subjected to the 'suction pressure of said compressor for controlling the number of cylinders in operation in accordance with the suction pressure of the system and a second valve rod operator including a part subjected to the temperature of the medium cooled by said system for controllingthe number of cylinders in operation by the temperature created by said system, the one of said valve rod operators controlled by the temperature created by said system being stronger than the other oi' said valve rod operators so as to exert the greater i influence on said valve rod. 6. A cooling system comprising a compressorcondenser-evaporator system of refrigeration, the compressor of which comprises a plurality of cylinders and means to vary the number of cylinders compressing rei'rigerant comprising individual cylinder unloading means associated with each of a number of said cylinders, fluid pressure means for operating said individual cylinder unloading means lncluding a master valve having a valve rod capable of being moved to a number of control positions to vary the number of said individual cylinder unloading means operatively connected to said fluid pressure means, and dual means for selecting the control position to which said valve rod is moved comprising a rst valve rod operator including a part subjected to the y suction pressure of said compressor for controlling the number of cylinders in operation in accordance with the suction pressure of the system and a second valve rod operator including a part subjected to the4 temperature of the medium cooled by said system for controlling the number of cylindersin operation by the temperature created by said system, the one of said valve rod operators controlled by the temperature created by said system being of greater strength than the other of said valve rod operators so that normally controlv of said unloading means is solely under the influence of the temperature of the medium.

7. A cooling system comprising a compressorcondenser-evaporator system of refrigeration, the compressor of which comprises a plurality of cylinders and means to vary the number of cylinders compressing refrigerant Vcomprising individual cylinder unloading means associated with each of a number of said cylinders, iiuid pressure means for operating said individual cylinder unloading means including a master valve having a valve rod capable of being moved to a number of control positions to vary the number of said individual cylinder unloading means operatively connected to said iiuid pressure means, and dual means for selecting the control position to which said valve rod is moved comprising a first valve rod operator including a part subjected to the suction pressure of said compressor for controlling the number of cylinders in operation in accordance with the suction pressure of the system and a second valve rod operator including a part subjected to the temperature of the medium cooled by said system for controlling the number of cylinders in operation by the temperature created by said system, the one of said valve rod operators controlled by the temperature created by said system being of greater strength than the other oi said valve rod operators so that normally control of said unloading means is solely under the inuence of the temperature of the medium, but each of said valverod operators being complete and capable of independent action so that `control of the compressor will be assumed by the one of said valve rod operators controlled by the suction pressure in the e'vent of failure of the valve rod operator controlled by the temperature of the medium.

RAFAEL A'. GONZALEZ. 

